Hi everyone!
The idea is to run a "CityEL" (an old three wheeled electric car weighing ~300kg incl. me and a top speed of 50 km/h) off of a VESC 4.12 I've already got.
Currently it's driven by a brushed motor, and I'd like to replace it with a BLDC motor and a VESC because the brushed motor is heavy, inefficient and very noisy.
The plan is to run motor currents of 120A (possibly 150A) through the VESC during acceleration, and because of that to submerge the VESC in oil with a circulation pump and a heat exchanger on an aluminum part to keep it at a moderately healthy temperature. I've got all the parts needed for this lying around waiting to put to use...
It's running on an 11s Li-Ion battery that's never charged above 3.95V/cell, so the VESC should be safe voltage wise.
The motor and gearing part I have figured out so far, what I need help with is the motor speed/brake control:
The CityEl right now has a latching forward/reverse switch (it's also switching the reverse light) and a 5k Ohm gas potentiometer.
The easiest to build and imo most comfortable way to run the VESC in a CityEL would be to have a control App that allows one-pedal driving (braking from 0-30% throttle range, accelerating from 30-100% range or similar with an output for the brake lights), and reversing as long as the switch is on reverse. Unfortunately I don't know how to program. :D
So right now I'm planning to run the VESC in "Current Reverse ADC2 Brake Button" mode, with a second potentiometer added to the braking pedal and the forward/reverse switch replaced by a momentary button, and a relay that's switching the reverse light on and off when the button is pushed.
Does anybody have a better idea? Also, I'd be willing to pay 50 € if someone could program a control app for one pedal driving (don't know if this is a reasonable offer, but I can't really put more money into it...).
Regards!
Matthias
"The plan is to run motor currents of 120A (possibly 150A) through the VESC during acceleration, and because of that to submerge the VESC in oil with a circulation pump and a heat exchanger on an aluminum part to keep it at a moderately healthy temperature. I've got all the parts needed for this lying around waiting to put to use... "
Not sure it's a good idea, because oil will become conductive after some time!
Someone has soldered a heatpipe taken from a PC CPU cooling system, and it seems to work well.
For the App, there are a lot of things available with the latests versions, see also Ackmaniac's ESC Tool, are you sure that one will not fit your bill?!
Hope this helps.
Have a Nice Day.
Thierry
Thank your for pointing me in this direction! On the other hand, people have been cooling their PCs with oil for ages... I'll look into what people are using and what might be the best oil to use, also I'll make sure the system is absolutely airtight. Do you have an idea what type of oil might be best? It's just that I think taking away the heat directly using a liquid is the best way, because I also might not stop at 150 A... I'll leave the oil I put in there on the shelf and measure resistance from time to time.
I've had a look at Ackmanics stuff, not what I'm looking for unfortunately!
To you too,
Matthias
I'd say that going above 150A is not a good idea.
Normally there is a big margin between the motor current and the max-according-to-the-manufacturer of the FETs. In the case of the VESC4, about a factor of 8.
The VESC6 uses FETs that can handle 200A under best-case conditions. So even 120A is WAY closer to the limit that the manufacturer states than with the VESC4.
Okay... Well, the VESC probably can't read currents this high anyway, so I'll leave it at 150A :D I know that this is way above any recommendation, but I'm curious about the limits too... :)
Also I'm a little worried the shunts might solder themselves out, if I would only cool the FETs...
Oil won't do magic. Check the datasheet, those mosfets dissipate well from the pcb side, not on the epoxy side, and v4 has the mosfets back to back, trapping the heat into the pcb. You will have better chances with a vesc 6 (rated at 80A IIRC). Mineral oil is a worse coolant than water, and I would be a bit worried about the dielectric strength and pollution degree of such liquid in contact with the power electronics.
oil is used in "high isolation required" situations. If you use the right oil I'm pretty sure you'd be able to cool the PCB just next to the FETs a bit better than before so that you get slightly improved performance. But changing the layout is even better. (and e.g. cool the backside of the PCB with lots of vias to conduct the heat. )